Hi There. Happy new year for everyone and thank you in advance for reading my question and honest your opinions.
My 08 S40(I just bought last month and I don't know service history) is backfiring when I rev up at idle(not driving) when I went for safety test, mechanic told me I should clean up Carburetor.
I can clean up Carburetor but I am thinking about something else shortcut way. Is it work if I drain gas from gas tank pour carb/injector cleaner (it is not gas additive) run engine? Do you think it will clean up deposit or gunk? Normally I used this carb/injector cleaner for cars which I directly connect to fuel injector after disengage fuel pump. Please let me know what are you thinking thank you.

Using carb cleaner is a hit or miss, you can try pouring it in and going for a ride but it may not work. I have never been lucky with gas additives.
Pulling the float of the carb is real easy on the savage, id do that then pull the pilot and main and clean them with carb cleaner spray.

What exhaust and air cleaner are you running?

If the backfire occurs when you open the throttle quickly and build up revs.....then let the throttle slam shut - get used to it, as it will always do that (and there really isn't any reason to do that with your engine....be kinder/gentler with how you open and close the throttle and the Savage engine will respond much better).  The Savage engine doesn't respond well to rough treatment.  When you close the throttle you are shutting off the fuel flow and a lean mixture is entering the engine....and the mixture is so lean the spark plug will not ignite the mixture.  As the engine slows down and the high vacuum stops pulling an excess amount of air through the carb....the engine will again begin to run and it will ignite all the unburned fuel/air mixture in the exhaust system and you will get a loud pop/bang in the exhaust.  If your engine is running lean the explosion will be louder than a bike that has a proper mixture - but they will all bang with when you rev them and let the throttle close (ever notice all the Harley's popping and banging as the "bikers" arrive on the scene revving their engines?).

Using carb cleaner is not likely to do much good - if the carb has been subject to the effects of the ethanol fuel....the problem is more likely to be corrosion than it is to be just gummed up.  A proper cleaning and jetting is in order.



Don't be this guy!

https://www.youtube.com/watch?v=Lt8F9QP-Azw

Sea Foam Works in my world.

Thank you all. I decide to clean Carb and also want to replace spark plug too. Removing Carb was easy but I can't drain gas from gas tank . I turned to PRI and nothing is coming out. What should I do now please let me know thank you.

I think Vercy means you might have turned it the wrong way, look on the lever ,there is an arrow.